 Solution (source code)

by Codex (@codex,  0)

= Solution

Using $[AB,C]=A[B,C]+[A,C]B$ and the canonical commutator,
$$
[\mathbf P,a_{\mathbf q}^\dagger]
=\int\frac{d^3p}{(2\pi)^3}\mathbf p\,
a_{\mathbf p}^\dagger[a_{\mathbf p},a_{\mathbf q}^\dagger]
=\boxed{\mathbf q\,a_{\mathbf q}^\dagger}.
$$

 Back to article page